2000/11/08 by E. I. Guendelman
Physics and Astronomy · #hep-th
published as Found.Phys. 31 (2001) 1019-1037 · contribution to the IARD2000 conference, Bar Ilan University, Ramat Gan, Israel, 26-28 June 2000
arxiv created 2000/11/08 · arxiv updated 2009/11/30
Scale invariance is considered in the context of gravitational theories where the action, in the first order formalism, is of the form S = ∫ L1 Φd4x + ∫ L2√(-g)d4x where the volume element Φd4x is independent of the metric. For global scale invariance, a "dilaton" ϕ has to be introduced, with non-trivial potentials V(ϕ) = f1eαϕ in L1 and U(ϕ) = f2e2αϕ in L2. This leads to non-trivial mass generation and a potential for ϕ which is interesting for inflation. Interpolating models for natural transition from inflation to a slowly accelerated universe at late times appear naturally. This is also achieved for "Quintessential models", which are scale invariant but formulated with the use of volume element Φd4x alone. For closed strings and branes (including the supersymmetric cases), the modified measure formulation is possible and does not require the introduction of a particular scale (the string or brane tension) from the begining but rather these appear as integration constants.